Conventionally, this type of synthetic resin grommet is usually composed of a grommet main-body having locking claws such as wings, ribs or the like obliquely, and upwardly formed on the side thereof (refer, for example to Japanese Utility Model Application No. Sho 60-18314).
However, the conventional grommet has some problems. That is, since the locking claws are formed along the body of the grommet itself, the body is difficult to flex because the claws are relatively rigid. Consequently the grommet cannot be easily inserted well into a member to be attached. Additionally the conventional grommet has poor water-proof sealing properties, and when the grommet is inserted into the member to be attached, a chattering is caused therebetween. The chattering results from a gap left between an upper end of the locking claws and the member to be attached. The chattering lasting generally until a tapping screw is tapped into the grommet main body to fix it in place.